In mobile communication systems, much research on Self-Organizing Networks (SON) for autonomous setting of communication parameters for wireless base stations is being conducted due to the complexity of wireless network operations. One of the objectives of SON is to optimize coverage (in other words, a service area) by using wireless base stations.
Coverage can be optimized in SON by eliminating blind zones (coverage holes) by adjusting the tilt angles of wireless base station antennas or by adjusting the transmission power and the like when, for example, such coverage holes where radio waves do not penetrate properly are present. To optimize coverage in this way, SON administration servers and the like in the wireless base stations or in the system need to understand the coverage conditions such as the presence of coverage holes for adjusting the tilt angles or transmission power.
Related art documents indicated below describe a technique of receiving reports of signal strength of wireless terminals measured by the host wireless base stations, and then detecting coverage holes based on the signal strength. Additionally, techniques for adjusting wireless base station communication parameters such as the tilt angles to eliminate detected coverage holes, and then determining the optimization results from wireless conditions after the adjustments are also mentioned.
Japanese Laid-open Patent Publication No. 2008-172380 is an example of related art.